US2333676A - Adhesive composition - Google Patents

Description

Patented Nov. 9, 1943 2,333,676 ADHESIVE COIWPOSITION John E. Robinson, Glen Ellyn, Ill., assignor to American Can Company, New York, N. Y., a corporation of New Jersey No Drawing. Application February 21, 1941,

Serial No. 380,068

' 2 Claims. (01. 260-27) The present invention relates to a special adhesive which is adaptable for use with fibrous materials or other substances to provide tight seams or joints which will not pull loose or open up when subsequently subjected to ordinary temperatures or to reasonable handling, and the invention has particular reference to thermoplastic cement or adhesive made up of resins properly mixed together and without the use of solvents.

Vinyl and other resins have been used in adhesives in connection with suitable solvents. A prolonged drying time is required to dry oil the solvents. Where the adhesive is used on fibrous material it is necessary to subject the fibre or paper to the heat of drying. This drying is in- Jurious to the paper because the time and temperature required materially reduce'the moisture content of the paper, making it lifeless. Such drying also distorts the paper out of shape and this presents problems of proper handling. There is also consequent waste of materials.

There is another serious difiiculty in the use of solvent adhesive where the paper stock containing the adhesive is involved in the manufacture of containers for food products. Under commercial drying conditions for fibrous stock there is always the danger of some solvent being trapped and not properly eliminated. The result is a more or less vital danger of oil-taste andodors in the food content as imparted by any slight traces of improperly dispersed solvent.

High speed production, the modern essential of manufacture, accentuates the problems. In the interest, of time saving higher drying heats are employed and the difficulties are multiplied many times.

The present invention contemplates the production of a thermoplastic adhesive withoutthe use of solvents of any kind and includes the mixing together of resinous ingredients at elevated temperatures as by a kneading action. 'Such an adhesive when used on fibrous material does not require any destructive drying out or elimination of moisture from the fibrous stock and there being no solvents the problem of imparted oiltaste or odors is not present.

An object of the invention is the provision of a method of preparing a special thermoplastic adhesive for use on fibrous materials to hold the fibrous parts in close bonded relation and to pressed together.

the use of a mixture of vinyl resin and a pentaerythrityl-abietate resin.

Yet another Object is the provision of steps for a method of manufacturing fibrous containers for food stuff and the like in which a thermoplastic adhesive is used which will not impart an olitaste or an odor to the product packed in the finally completed container.

Numerous other objects and advantages of the invention will be apparent as it is better understood from the following description which is of a preferred embodiment thereof.

The thermoplastic adhesive of the present invention may be used in the manufacture of fibre containers such as shown, for example, in the J. M. Hothersall Patent Number 2,085,979, issued by the'United States Patent Oflice on July 6, 1937, and such a use will be hereinafter referred to as it provides an excellent example for showing many of the advantages inherent in the thermoplastic adhesive of the invention.

In the Hothersall container the body is formed into tubular shape and the edges of the fibre blank from which the body is made are brought together in lapped relation. A sealed joint is made of these lapped parts by squeezing them together with the thermoplastic adhesive interposed between the laps. At the time of sealing the adhesive is-in heated or plastic condition and while tacky, the overlapped edges are firmly This may be done by suitable die parts, rollers or the like which may be heated or cooled as required in order to produce the desired bond of the fibre sections. The ends of the Hothersall container are similarly secured to the body.

After this forming of the adhesive joints the container is liquid proofed by immersion in melted parafiin which may be maintained at as high a temperature as 190 F. The seams are in direct contact with the hot liquid and are subject to the high temperature, sometimes for an appreciable length of time. The thermoplastic adhesive of the present invention withstands such drastic action and the joints secured thereby remain tight and are unaffected. This example of one use of the present adhesive presents a concrete picture which it is believed will shown some of the problems which are solved by this special adhesive.

The thermoplastic adhesive of the present invention in a preferred form consists of a mixture preferably about percent of polyvinyl resin such as vinyl acetate and 30 percent of pentaerythrityl-abietate resin, such as that disclosed in the Leavitt N. Bent and Alan C. Johnston Patent 1,820,265, issued by the United States Pattent Ofiice on August 25, 1931.

In making up the thermoplastic adhesive some consideration must be given to the use for which the adhesive is intended and will be subsequently employed. In providing a thermoplastic adhesive suitable for the manufacture of the Hothersail container previously referred to by way of example, this adhesive is made up by mixing together the ingredients under a proper heat.

The vinyl resin and the pentaerythrityl-abietate resin are put into a mixing mill where they are held at temperatures varying from 250 F. to 350 F. While being completely kneaded and thorougly mixed for substantially fifty or sixty minutes. The resulting mixture is kept hot being at such a time ina viscous, fluid state. As such it is in satisfactory condition to be applied to the v fibrous surface. For applying to one or more of the surfaces to be secured together, the adhesive is preferably introduced into a tank or suitable vessel which is maintained at a temperature of from 350 F. to 450 F. Application to the surface of fibrous stock for example may be made by passing the stock over adhesive applying rollers which may be located in the tank and which are caused to rotate in the heated liquid.

The adhesive when applied as a thin film on the fibrous surface will set or harden substantially at once. Artificial cooling may be used if desired but it is believed for practical commer cial purposes that artificial cooling will hardly ever be necessary.

Continuing with the example of manufacture of the Hothersall can, the edges of the blank to which this adhesive has been applied will next be brought together. This may be between heated surfaces or the adhesive may be softened by heat and the joint made under a pressure exerted in suitable manner as by dies or rollers. This forms the seal or tight joint desired and the pressure members may then be immediately backed 01? or removed from the body.

Other materials may be added to the resinous.

ingredients entering into the thermoplastic cement if desired but such additions will not be in the nature of solvents. Different quantities of gums may also be used other than the proportions given. I

It is thought that the invention and many of ,its attendant advantages will be understood from the foregoing description, and it will be apparent that various changes may be made in the steps of the process described and their order of accomplishment without departing from the spirit and scope of the invention or sacrificing all of its material advantages, the process hereinbefore described being merely a preferred embodiment thereof.

r I claim:

1. A process of preparing a thermoplastic adhesive designed to permanently seal the joints of containers constructed of fibrous material which will not give way when subjected to immersion in molten coating material at a temperature of substantially 190 F., consisting in thoroughly mixing substantially percent polymerized vinyl acetate with substantially 30 percent of pentaerythrityl-abietate resin while maintaining the mixture at a temperature of from 250 F. to 350 F., whereby said mixture is suitable for subsequent application to the said container joints at a temperature of from 350 F. to 450 F.

2. A composition of matter suitable for application as an adhesive at a temperature of from 350 F. to 450 F. to secure the joints of a container constructed of fibrous material,.said composition consisting of a mixture of substantially f 70 percent of vinyl acetate and substantially 30 percent of a pentaerythrityl-abietate resin, whereby to insure retention of the adhesive char acteristics of said composition when the container is subjected to a temperature of substantially F., as for example, when passed through a bath of molten coating material to render the container liquid proof.

JOHN E. ROBINSON.